The creation of virtual networks using overlays has become a pervasive practice in the networking space. The industry offers diverse, and often incompatible, solutions. There are mainly two categories of solutions based on the control plane model employed: controller-based and protocol-based. Controller-based solutions employ a central database from which host reachability information is pushed to tunnel end-points of a virtual network. Examples of controller-based solutions include, for example, Cisco Virtual Topology System (“VTS”) and VMware NSX virtual networking solutions and their use of OVSDB and OpenFlow with its vendor-specific extensions. Protocol-based solutions employ a distributed model in which all involved network elements participate in a well understood protocol to calculate and disseminate the relevant reachability information. Examples of protocol-based solutions include, for example, BGP-EVPN overlays and LISP Overlays. Controller-based and protocol-based solutions are inherently incompatible due to the manner in which each distributes reachability and data plane encapsulation capability information.
MAC/IP routes need to be learned for EVPN. EVPN solutions require MAC/IP routes (also referred to as EVPN Type 2 routes or “RT-2”) to be learned as soon as possible to advertise/establish reachability for connected hosts. Additionally, for host virtual machines (“VMs”) multi-homed via a Multi-Chassis Link Aggregation Group (“MC-LAG”) interface to redundant ToR switches that act as first hop IRB gateways between the MC-LAG access and an EVPN-Multiprotocol Label Switching (“MPLS”) overlay network, host VM layer 3 (“L3”) adjacency (learned on the IRB L3 interface) and host VM MAC (learned on the access LAG) must be synced across redundant ToR switches in order to achieve optimal all-active multi-homing with overlay Equal Cost Multipath (“ECMP”) paths and local switching.
This MAC+IPV6 L3 adjacency sync and MAC sync are accomplished via special handling of received EVPN MAC+IPV6 RT-2 advertisement pertaining to a dual-homed host. This special handling identifies the received RT-2 to be that on a locally connected Ethernet Segment Identifier (“ESI”) and as a result, creates a synced local adjacency and a synced local MAC entry for the dual-homed (or multi-homed) host in the event that the host has not been learned dynamically via IPV6 neighbor discovery (“ND”) protocol. This enables redundant IRB gateway (“IRG-GW”) ToR switches to be able to forward routed and bridged traffic directly towards a locally connected host irrespective of which of the redundant ToR switches learned the ND entry and MAC natively, and hence provide optimal ECMP forwarding paths to a host over EVPN overlay.